Method of producing a detergent composition



' Patented u e. 24, 1

1 U TED -mirnon or rnonucmo a DETERGENT ooMrosmoN Frederick c.Bersworth, erona, N. .1.

No Drawing. Application June 9, 1944, Serial No. 539.595

' 2 Claims. (01. 252-117) This invention relates to detergentcomp'ositions and more particularly to detergent compositions suitablefor use in hard, saline, and hardsaline water, and is an improvementinvention of the invention described'and claimed in copendingapplication Serial No. 539,595, filed June 9, 1944, which application isassigned to the same assignee as the present invention.

One of the objects of the present invention is to provide a detergentcomposition for use in hard, saline, and hard-saline water.

Another object is to provide a composition having detergent anddeionization properties for use alone or in combination with alkalimetal-fatty acid soap compounds in hard, saline and hardsaline water.

Still another object is to provide a deionlzation agent compatible withalkali metal-fatty acid soap compounds in aqueous solutions.

Other objects will be apparent as the invention is more fullyhereinafter disclosed.

' In accordance with the disclosure of my copending application SerialNo. 539,595, above noted, I have discovered that the only alkali metalsalts utillzable as deionization agents and electrolyte-carrying agentswith alkali metalfatty acid soap compounds in aqueous solutions are theacid-alkali metal salts of the aliphatic amino polycarboxylic acids,particularly those amino acids containing more than two carboxylic acidgroups attached directly to amino nitrogens, such as the acid-alkalimetal salts of ethylene diamine tetracarboxylic acid which in molarweight aqueous solution have a PH between 7 and 9.5, preferably thosehaving a pH of approximately 8,

In accordance with the present invention 1 form a detergent compositionconsisting of an equilibrium mixture of the acid-alkali metal salt ofthe amino acid, particularly ethylene dianiine tetracarboxylic acid, anda mono-basic fatty soap acid, such as stearic acid, in aqueous solutionhaving a pH within the range '7to 9.5 but preferably approximating a pHof about 8, by saponifying the fatty acid in an aqueous solution of thetetra alkali metal salt of the amino-acid until the pH of the solutionapproximates 8 or is within the range 7 to 9.5.

This equilibrium solution of amino acid, fatty acid and caustic alkali,having a pH of about 8, is a detergent composition suitable for use inhard water of various de rees of hardness, in water containing neutralelectrolytes such as sodium chloride or sodium sulfate, and also inhard-saline water such as sea water. The said equilibrium 2 solution isalso miscible in all proportions with alkali metal-fatty acid soapcompounds to form a plurality of detergent compositions that are alsosuitable for use in hard water'of various derees of hardness, in watercontaining strong neutral electrolytes, and in hard-saline water, suchas seasvater.

As a specific embodiment of this invention, but not as a limitationthereof, the invention will be described as it has been adapted to theforma tion of a detergent composition consisting of an equilibriummixture of an acid-alkali metal salt of ethylene diamine tetracarboxylicacid and the alkali metal salt of stearlcacid. In this example anaqueous solution of the tetrasodium salt of ethylene diaminetetracarboxylic acid containing one molar weight (or 380 grams) in 3%liters of water (3500 c; c.) having 9. PH of about 10.5 is digestedunder a reflux condenser with 1 /2 molar weights (427.5 grams) ofstearic acid, at elevated temperatures approximating the boiling pointof the solution for an extended time interval until the pH of thesolution approximates 8. The resulting solution is filtered while hot,to remove therefrom any unsaponifled fatty acid, and then is cooled toatmospheric temperatures. At atmospheric temperatures the solutionsolidifies to a substantially transparent jelly which is 'completelysoluble in cold or warm water.

To materially shorten the time interval of heatms to obtain thesaponification ofthe stearic acid by the free alkali present in theaqueous solution of the tetra salt, the solution may be heated in anautoclave under a pressure of steam approximating 20 pounds.

The chemical reaction involved in this process is essentially one ofsaponification of the stearic acid by the caustic alkali set free inaqueous solution by ionization of the tetrasodium salt of the aminoacid. This salt in aqueous solution has a pH of about 10.5 and, inaccordance with my experiments, the tetra salt in aqueous solutions ofabout this concentration hydrolyzes with liberation of two molecules ofcaustic alkali per molecule of tetra salt present. Stearic acid, in anamount somewhat in excess of that approximately suihcient to combinewith one of the molecules of caustic alkali liberated by the tetra salt,is preferably employed, to shorten the time interval of heating requiredto obtain, by saponiflcation of the stearic acid, a lowering of the pHof the solution to the desired figure of pH 8 within the range 7 to 9.5.

The saponiflcation reaction proceeds to an equilibrium compositionconsisting essentially oi the acid-trisodium salt of reaction time andreaction pressures, as one v skilled in the art may perceive.

Alternatively, I may form substantially the same detergent compositionby digesting at elevated temperatures, one molar weight of the aminoacid and 1 /2 molar weights of the stearic acid in an aqueous causticalkali solution of the same approximate volume containing about 4 molarweights of caustic alkali (NaOH), until a solution having a pH ofapproximately 8 is obtained.

The detergent composition obtained by the practice of the abovedisclosed method is miscible in all proportions with alkali metal-fattyacid soap compounds to form detergent compositions suitable for use in aplurality of different types and kinds of hard waters,electrolyte-carrying waters and in hard-saline waters.

As an illustration, in accordance with usual laundry practice a soasolution containing 10 to 15% alkali metal-fatty acid soap compounds isusually employed to which soap solution various water softening agentsin proportion to the hardness of the water being used may be added toform a stock soap solution. In accordance with the present invention,from to (dry weight) of the detergent composition of the above speciflcexample, based on the weight of the soap compounds present in the soapsolution, is added to the soap solution for use with medium to hardwater; from 10 to of the composition is added for use with hard to veryhard water and with water containing moderate amounts of electrolytes;and from 15 to of the composition is added for extremely hard water orfor water containing relatively large amounts of electrolytes and forhard-saline water, such as sea water.

The addition of the detergent composition of the present invention tosoap solutions or to solid and liquid soap compounds presents noparticular problem as the detergent is miscible in all proportions withsuch soap compounds. In general, identically the same practice as hasheretofore been followed in the soap art is followed in the forming ofbar, flake, powder, or liquid soap compositions including the detergentcomposition of the present invention or in the forming of concentratedaqueous soap solutions.

In the adaptation of the present invention to the forming of detergentcompositions consisting of a mixture of the acid-alkali metal salts ofany of the other aliphatic amino polycarboxylic acids heretoforerecognized in the art as strong deionizing agents and the alkali metalsalt of a. soa fatty acid, substantially the same procedure is watersoluble alkali metal salts of the fatty acid, thereby lowering the pH ofthe solution to within the range 7 to 9.5 and preferably to a pH ofabout 8. The precise amount of fatty acid required to obtain thisdesired result will vary with respect to variation in the amount of freealkali liberated by the amino acid salt in aqueous solution or presentin the solution in addition thereto.

In place of a soap fatty acid, I may also employ a large number of otherorganic acids, such as the di-basic acids and poly-basic acids toneutralize the free alkali of the solution and to obtain Variousequilibrium mixtures having a pH within the range specified which, whilenot necessarily being detergent compositions, are miscible in allproportions with alkali metal-fatty acid soap compounds to form adetergent composition containing the deionizing and electrolytecarryingacid-alkali metal aliphatic polycarboxylic acid complex of thepresentinvention and of the invention of my co-pending applicationBerial No. 539,595, above identified.

Having hereinabove described the present invention generically andspecifically and given one specific example of the same, it is believedapparent that the same may be widely varied without essential departuretherefrom and all such modifications and adaptations of the same arecontemplated as may fall within the scope of the following claims:

What I claim is:

1. The method of forming an aqueous solution containing about one molarweight of the trisodium salt of ethylene diamine tetracarboxylic acidand about 1 molarweight of the sodium salt of stearic acid whichcomprises dissolving about one molar weight of the tetrasodium saltfollowed as hereinabove described, namely thev aqueous solution of thefully neutralized salt of the amino acid is digested with the said fattysoap acid until the free alkalicontent of the aqueous solution has beensubstantially removed therefrom by reaction with the said fatty acid toform of the said amino acid in a volume of water, adding thereto about 1/2 molar weights of stearic acid, and heating the solution for anextended time interval until the pH of the solution is stabilized at apH of about 8, and filtering the solution while hot to remove the excessstearic acid present therein.

' 2. The method of producing a detergent composition consisting of awater soluble mixture of an acid alkali metal salt of an aliphatic aminopolycarboxylic acid having more than two carboxylic acid groups attacheddirectly to amino nitrogens with at least one of the carboxylic groupsin excess of two unneutralized by alkali metal and an alkali metal saltof a monobasic fatty soap acid, which comprises forming an aqueoussolution of the fully neutralized alkali metal salt of said amino acid,adding thereto the monobasic fatty soap acid in such an amount requiredto combine with at least one of the alkali metal ions of each moleculeof the salt of said amino acid and to lower the pH of the solution to apH within the range '7 and 9.5, heating the solution for an extendedtime interval to solubilize the mono-basic fatty soap acid as the alkalimetal salt of mono-basic fatty soap acid, and filtering the solutionwhile hot to remove the excess monobasic fatty soap acid presenttherein.

FREDERICK C. BERSWORTH.

